More girls may be in NSW sex ring

Police fear more young girls may have been victims of a child prostitution ring in Sydney and are too frightened to come forward.

One of the girls who was enticed into having sex in cars and motels with male clients was 13, police will allege.

Officers of Strike Force Woodvale arrested a 22-year-old woman at Warwick Farm, in the city's southwest, at about 8.30am (AEDT) on Friday and charged her with armed robbery and child prostitution offences.

Liverpool crime manager Danny Doherty said the woman preyed on girls living on the street and in refuges for the homeless.

"These girls may be too scared to come forward or may be traumatised by the acts, but I urge them to contact police so they can get the necessary support they need," Detective Inspector Doherty said.

Police suspect the woman lured at least three girls into the prostitution ring that operated for about three months.

She allegedly contacted her clients by phone and arranged for them to meet the girls in cars and motels.

"It's a sad reflection on society when you've got a 22-year-old woman soliciting and making money out of kids as young as 13," Det Insp Doherty said.

Detectives are yet to determine how she advertised, but they believe she offered the sexual services of young girls.

"It's obviously very unusual for a young woman to be arranging other young women to engage in acts of prostitution," Det Insp Doherty said.

Police also allege the woman was involved in an armed robbery of a person in February.

She was charged on Friday with promoting child prostitution, obtaining benefit from child prostitution and armed robbery.

The woman was refused police bail and is to appear in Parramatta Bail Court on Saturday.

Anyone who may have been a victim of the alleged prostitution ring or anyone who has information about the matter is urged to call Crime Stoppers on 1800 333 000.